Longitudinal Loading Phase

The third and final loading sequence involved application of a load in the direction of the longitudinal axis of the ROPS。 A 50 tonne hydraulic ram was used to apply the necessary longitudinal load to the midpoint of the horizontal beam that linked each post。 As before precautions were taken to ensure load spreading and to alleviate any eccentric loading of the jack。  The  load  deflection  behaviour  was  almost  linear  and  under  full  longitudinal load

indicated a maximum longitudinal deflection of 33 mm with a residual (permanent) deflection of 13mm upon removal of the load。 During this loading phase, the ROPS also underwent deflection in the lateral direction of approximately 20mm with a permanent deflection of 7 mm。

A Comparison of experimental and FE results under vertical and longitudinal loads is discussed in the next section。 But it has to be noted that these two loading phases take place on the ROPS model which has already suffered significant plastic deformation after the initial lateral loading phase。 It is also important to note that the lateral loading phase is the most important phase, which is also the focus of this paper。 The other two loading sequences are strength cases to ensure that a ROPS has adequate capacity in the vertical and longitudinal directions。

Summary of Experimental Testing

Though this ROPS successfully passed the requirements of the Australian standard, the stiffness distribution was low and this ROPS was more flexible than expected。 The energy requirement for this ROPS was fulfilled with a low force/ high deflection response。 Despite the formation of hinges at the described locations during lateral loading, the ROPS possessed sufficient capacity to withstand the subsequent vertical and longitudinal loading sequences without violation of the DLV。 It has been shown that ROPS models may be tested using the procedures outlined in the current Australian Standard for Earthmoving machinery AS2294。2-1997。

Finite Element Analysis of K275 Bulldozer ROPS

A detailed three dimensional finite element model of the ½ scale ROPS that accurately reflected the correct stiffness distribution of the ROPS, based on the results of the similitude study, was developed。 The program ABAQUS standard v6。3 which is a general purpose

FEA package with the ability to model both linear and highly nonlinear structural problems was used in the analysis。 The pre and post processing software package MSC Patran 2004 was used to construct the finite element models and visualise the results after each FE computer simulation。 The QUT’s Super Computer, Sirius, which uses an IRIX operating system was employed to run all of the necessary ABAQUS models。

Numerical simulation under the static force requirements of AS2294。2-1997 was carried out and the computer model was validated by comparing the experimental and numerical lateral load vs deflection profiles。 This validation enabled further FE analysis and to determine whether FEA can be used as a valuable tool for certifying ROPS and thus lessening the need for destructive full scale testing。 A similar full scale FE model of the ROPS was also developed and analysed and the established similitude relationships between the full and ½ scale ROPS were verified。 This is discussed in the next section。 The full scale FE ROPS model can then be used in further investigations。

Properties

ABAQUS S4R shell elements with dimensions of 10 and 5 mm (representative of mesh densities) were used to model the full and half scale ROPS models respectively。 Shell thickness of 10mm and 5mm were used in the full and half scale FE ROPS models respectively。 Figure 8 shows the FE model of the full scale prototype ROPS in which the FOPS has been omitted。

The material properties used for the FE models were based on uniaxial tensile tests on specimens taken from the same 350 grade RHS/SHS and the mild steel plate that was used to construct the ROPS and associated chassis beam and then converted into true stress and plastic strain suitable for input into ABAQUS。 Figure 9 shows the engineering stress strain